N-substituted derivatives of morphinan and uses thereof

ABSTRACT

The invention is based in part on the discovery that nonselective κ agonists that possess μ receptor-mediated effects in addition to their κ agonist effects can decrease cocaine self-administration more effectively and with fewer undesirable side effects than can highly selective κ agonists. The invention includes a number of new compounds having both nonselective κ opioid receptor agonist activity and additional activity at μ opioid receptors. These compounds are useful for the treatment of cocaine abuse, and can also be radiolabeled for use as imaging agents, e.g., the N-fluoroalkyl and iodoalkyl derivatives can be used, respectively, for positron emission tomography (PET) and single photon computed tomography (SPECT) brain imaging.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application 60/312,682filed Aug. 15, 2001.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under grant numbersK05-DA00360, U-19-DA11007, and K05-DA00101, awarded by NationalInstitute on Drug Abuse. The Government has certain rights in theinvention.

FIELD OF THE INVENTION

This invention relates to N-substituted morphinan compounds and usesthereof.

BACKGROUND OF THE INVENTION

The abuse of cocaine and other stimulant drugs is a significant socialand public health concern throughout the world (Crome, Drug AlcoholDependence, 55:247, 1999). Drug abuse has contributed greatly to theincreasing spread of HIV and HBV (Sorensen et al., Drug AlcoholDependence, 59:17, 2000). Currently there are no efficacious medicationsfor the treatment of cocaine abuse (Mendelson et al., N. Engl. J. Med.,334:965, 1996; Carroll et al., J. Med. Chem., 42:2721, 1999).

Although the mesolimblic dopamine pathway is believed to play a primaryrole in mediating the locomotor, discriminative stimulus, andreinforcing effects of cocaine (Smith et al., Drug Discovery Today,2:322, 1999; Wingler, in “Cocaine Abuse: Behavior, Pharmacology andClinical Application,” Higgens, S. T., Katz, J. L., Eds., Academic: SanDiego, 1998, pp. 135-158, 1998; Kuhar et al., Trends Neurosci., 14:299,1991; Ritz et al., Science, 237:1219, 1987), other neurotransmittersystems have also been implicated in the reinforcing effect of cocaine(Walsh et al., Psychopharmacology, 130:41, 1997; Rocha et al., Nature:Neuroscience, 1:132, 1998; Giros et al., Nature, 379:606, 1996; Rocha etal., Nature, 393:175, 1998; Witkin et al., Life Sci., 53:PL405, 1993;Dewey et al., Synapse, 30:119, 1998; Negus et al., Psychopharmacology,152:398, 2000).

There is increasing evidence that opioid receptor agonists modulate theneurochemical and behavioral effects of cocaine. For example, kappa (κ)receptor agonists attenuate cocaine-induced increases in dopamine levelsin the nucleus accumbens (Maisonneuve et al., Neurosci. Lett., 181:57,1994; Heidbreder et al., NeuroReport, 5:1797, 1994). Administration of κopioid receptor agonists has also been reported to attenuate thediscriminative stimulus properties (Spealman et al., J. Pharmacol. Exp.Ther., 26:607, 1992; Spealman et al., Behav. Pharmacol., 5:21, 1994;Riberdy et al., Soc. Neurosci. Abstr., 21:718, 1995), conditionedreinforcing effects (Shippenberg et al., J. Pharmacol. Exp. Ther.,276:545, 1996; Shippenberg et al., Eur. J. Pharmacol., 345:27, 1998;Crawford et al., Psychopharmacology, 120:392, 1995), andself-administration of cocaine (Glick et al., Brain Res., 681:147, 1995;Mello et al., J. Pharmacol. Exp. Ther., 286:812, 1998; Schenk et al.,Psychopharmacology, 144:339, 1999; Negus et al., J. Pharmacol. Exp.Ther., 282:44, 1997; Kuzmin et al., Eur. J. Pharmacol., 321:265, 1997).Further, κ opioid agonists have been reported to attenuate thereinstatement of extinguished drug-taking behavior in an animal model ofrelapse (Schenk et al., Psychopharmacology, 144:339, 1999; Schenk etal., Psychopharmacology, 151:85, 2000). Taken together, these findingssuggest that activation of κ opioid receptors may functionallyantagonize some abuse-related effects of cocaine, possibly by inhibitingthe release of dopamine from dopaminergic neurons, and thus offers anovel and effective pharmacological approach to treat cocaine abuse.

SUMMARY OF THE INVENTION

The invention is based, in part, on the discovery that nonselective κagonists that induce μ receptor-mediated effects in addition to their κagonist effects can decrease cocaine self-administration moreeffectively and with fewer undesirable side effects than can highlyselective κ agonists. The invention includes a number of newmorphinan-3-ol compounds having both nonselective κ opioid receptoragonist activity and additional activity at μ opioid receptors. The newcompounds have relatively low affinity for the δ opioid receptor, and,thus, do not interact significantly with the δ receptor or produce sideeffects associated with activity at the δ receptor. These compounds areuseful for the treatment of cocaine abuse, and can also be radiolabeledfor use as imaging agents (e.g., the N-fluoroalkyl and iodoalkylderivatives can be used, respectively, for positron emission tomography(PET) and single photon computed tomography (SPECT) brain imaging).

In general, the invention features compounds of formula I for use invarious new methods described herein:

where R can be fluoropropyl (i.e., the compound can be compound 3 ofFIGS. 1A and 1B), isopropyl (compound 4), 2-ethoxyethyl (compound 5),2-methoxyethyl (compound 6), propargyl (compound 9),3,3,3-trifluoropropyl (compound 10), 3-cyanopropyl (compound 12),cyclopentylmethyl (20), furanylmethyl (22), thienylmethyl (23),3-iodoprop-(2E)-enyl (34), or 3-iodoprop-(2Z)-enyl (35), or a saltthereof. The compound can alternatively be any one of compounds 3, 5, 6,10, 12, 23, 26-31, 34, or 35 of FIGS. 1A and 1B, or a salt thereof.

In another embodiment, the invention features a single-photon computedtomography (SPECT) imaging reagent. The reagent can be labeled with aradioactive label, e.g., iodine, such as either ¹²³I-labelled compound34 or ¹²³I-labeled compound 35 (as shown in FIGS. 1A and 1B). Othercompounds of FIGS. 1A and 1B can also be labeled and used to preparesuch a reagent. The invention also features a method of SPECT imaging ofbrain opioid receptors (such as kappa opioid receptors). The methodincludes obtaining a new compound described herein, and labeling it withan appropriate label, e.g., an ¹²³I-labeled compound of FIGS. 1A and 1B,such as compounds 34 or 35, administering the labeled compound to apatient (e.g., by injection); and obtaining brain scans with a SPECTcamera to image, e.g., localize and/or quantify, the receptors.

In another embodiment, the invention features a positron emissiontomography (PET) imaging reagent. The reagent can be labeled with aradioactive label, e.g., fluorine, such as an ¹⁸F-labeled compound 3 or10 (as shown in FIGS. 1A and 1B), or compound 1. Other reagents can bemade from other compounds in FIGS. 1A and 1B labeled in the same way.The invention also features a method of PET imaging of brain opioidreceptors (such as kappa opioid receptors). The method includesobtaining one of the new compounds and labeling the compound to create,e.g., an ¹⁸F-labeled compound of FIGS. 1A and 1B, such as compounds 3 or10 as referenced herein, administering the labeled compound to a patient(e.g., by injection); and obtaining brain scans with a PET camera toimage, e.g., localize and/or quantify said receptors.

In still another embodiment, the invention features a method of treatinga patient addicted to cocaine. The method includes the steps ofadministering to the patient an effective amount of a compound offormula I; where R can be, for example, hydrogen (—H), alkyl,cycloalkyl, alkenyl, alkynyl, aryl, aralkyl, alkoxy, aryloxy,arylcarbonyl, cyanoalkyl, aminoalkyl, haloalkyl, haloalkenyl,α-hydroxy-aralkyl, or other substituted alkyl group; or a10-ketomorphinan analog thereof. For example, the compound can be anyone or more of compounds 3, 4, 5, 6, 8, 9, 11, 12, 34, or 35.

In still another embodiment, the invention features a method ofidentifying a drug useful for treating a patient addicted to cocaine.The method includes identifying a compound having nonselective κ opioidreceptor agonist activity and either μ opioid receptor agonist orantagonist activity. The invention also features a method of making apharmaceutical formulation by identifying a drug using the new methods,and then mixing the drug with a physiologically acceptable excipient toprepare the formulation. The invention also features a method oftreating a patient addicted to cocaine, by administering to the patientan effective amount of the drug, or the pharmaceutical formulationincluding the drug, identified by the above method.

As used herein, the term “agonist” refers to compounds that produce aphysiological effect mediated by a receptor.

As used herein, the term “antagonist” refers to compounds that bind tothe same receptors as do corresponding agonists, but do not produce thephysiological effect produced by the agonist. By binding to thereceptor, the antagonist can, for example, inhibit the binding of anagonist to the same receptor. Thus, the presence of the antagonist canprevent the production of the physiological effect even though theagonist is also present.

The “nonspecific” agonists of the invention bind with high affinity tomore than one type of opioid receptor, specifically, both κ and μ.

The terms “bonded,” “binding,” “binds,” or “bound,” as used herein, canrefer to, for example, covalent, ionic, van der Waals, or hydrophobicinteractions. Coordination complexes and hydrogen bonding are alsocontemplated. Typically, the bonding interactions are reversible, butcan be irreversible in some cases.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entirety. In case of conflict, the presentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

The invention provides several advantages. For example, κ agonists withvarying degrees of activity have fewer side effects than do κ-selectivecompounds. Activity at the μ receptor appears to decrease side effectssuch as sedation and dysphoria.

Because certain of the new compounds contain a group that can beradiolabeled, these compounds can be administered in very low quantitiesto humans for use in tomographic imaging of the brain, allowing thebinding of the compounds to different brain regions to be monitored. Anadvantage of using these compounds for PET and SPECT imaging is thatthey can enable determination of the localization and density of κopioid receptors in human brain tissue. The new compounds can also beuseful to determine if the amount of κ opioid receptor in brain changesas a result of cocaine use.

Other features and advantages of the invention will be apparent from thefollowing detailed description, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B together form a table of various N-substitutedmorphinans and their physical properties.

FIG. 2 is a reaction scheme illustrating three methods for the synthesisof N-substituted morphinans.

FIG. 3 is a reaction scheme illustrating the iododestannylation reactionused in the synthesis of N-(3-iodoprop-(2E)-enyl)morphinan 34 andN-(3-iodoprop-(2Z)-enyl)morphinan 35.

FIG. 4 is a table of binding affinities of the compounds of FIG. 1 forthe μ, δ, and κ opioid receptors.

FIG. 5 is a graph that illustrates the results of administering one ofthe new labeled compounds to a baboon, and imaging the distribution ofthe compound in the brain over time using SPECT imaging.

DETAILED DESCRIPTION OF THE INVENTION

A series of new N-substituted derivatives of morphinan were synthesized,and their binding affinity for three opioid receptors (i.e., μ, δ, andκ) was determined. A paradoxical effect of N-propargyl (MCL-117) andN-(3-iodoprop-(2E)-enyl) (MCL-118) substituents on the bindingaffinities for the μ and κ opioid receptors was observed. All of thesenovel derivatives showed a preference for the μ and κ versus δ binding.

To systematically study the effects of N-substituents in the morphinannucleus on binding affinity, selectivity, and efficacy at μ and κ opioidreceptors, a variety of substituents were introduced on the nitrogenatom in morphinan, and then the new derivatives were assayed forbiological activity. The κ/δ selectivity of most of these derivativeswas considerably better than that of levorphanol andethylketocyclazocine (EKC).

Chemical Synthesis

The target derivatives 3-13 and 20-31, shown in FIG. 1 were synthesizedfrom norlevorphanol 2 by one of the three methods as depicted in FIG. 2.Demethylation of levorphanol 1 was accomplished according to theprocedure reported by DeGraw and Engstrom (J. Labelled Compd. 11:233,1975). Thus, levorphanol was treated with ethyl chloroformate inrefluxing chloroform in the presence of K₂CO₃ followed by partialhydrolysis of the product with 10% NaOH in methanol. Norlevorphanol 2was obtained in good yield after hydrolysis of the resulting carbamate(structure not shown) intermediate in a mixture of hydrochloric acid andglacial acetic acid. Direct alkylation of norlevorphanol with variousalkyl halides in dimethyl formamide (DMF) using K₂CO₃ or NaHCO₃ as abase provided N-substituted derivatives 3-13 in good to excellent yields(all final compounds were characterized by NMR and mass spectroscopy,and gave satisfactory C, H, and N analyses, i.e., within +0.4% oftheoretical values).

In an alternative procedure, acylation of norlevorphanol with acidchlorides followed by reduction of the intermediate amide 14-19 withLiAlH₄ in tetrahydrofuran (THF) afforded the tertiary amines 20-25.

Alkylation of norlevorphanol with 1-aryl-3-(dimethylamino)-1-propanonemethiodide in DMF in the presence of Na₂CO₃ yielded ketones 26-28, whichwere then reduced with NaBH₄ to afford the alcohols 29-31 as a mixtureof hydroxy diastereomers. The N-(3-iodoprop-(2E)-enyl) andN-(3-iodoprop-(2Z)-enyl) derivatives 34 and 35 were obtained byiododestannylation of compounds 32 and 33 by treatment with iodine inchloroform. The reaction scheme is shown in FIG. 3. The tributyltinprecursors 32 and 33 were prepared by hydrostannylation of theN-propargyl derivative 9 with HSnBu₃ in the presence of Et₃B as catalystfollowed by column separation of the two isomers (see Goodman et al., J.Med. Chem., 37:1535, 1994). Another efficient route to the(E)-tributyltin precursor 32 involved alkylation of norlevorphanol with3-(tributylstannyl)prop-(2E)-enyl chloride, which was prepared bychlorination of 3-(tributylstannyl)prop-(2E)-en-1-ol with PPh₃ and CCl₄.The (E)-stannyl alcohol was obtained by hydrostannylation of propargylalcohol using the literature procedure of Emond et al., J. Med. Chem.,40:1366 (1997). The structures and physical properties of these newN-substituted derivatives are shown in FIG. 1.

Assays for Binding Affinity

The binding affinities of compounds 3-13, 20-24, 26-31, 34, and 35 forthe μ, δ, and κ opioid receptors were assessed using competitive bindingassays in guinea pig brain membranes employing [³H]DAMGO (μ agonist),[³H]naltrindole (δ antagonist) and [³H]U69,593 (κ agonist) asradioligands, using the methods described in Neumeyer et al., J. Med.Chem., 43:114 (2000). The results are summarized in FIG. 4. Forcomparison purposes, the binding data for U50,488, Mr2033, EKC,levorphanol, and cyclorphan are also included in FIG. 4. Antinociceptivebiological data can also be obtained using the tail-flick and/or mousewrithing tests (Id.).

Analysis of Data

The N-substituent has a significant effect on both the opioid receptorbinding affinity and selectivity of these morphinan derivatives. Forexample, our previous research indicated that replacement of the methylgroup in levorphanol with a cyclopropylmethyl group can greatly increaseaffinity at the δ and κ opioid receptors (20-fold and 40-fold,respectively), while the affinity at the μ opioid receptor increasesjust 2-fold (Id.). The N-cyclobutylmethyl analog MCL-101 showed 30-foldincrease in binding affinity at the κ opioid receptor, but the increasefor the μ and δ opioid receptors was less pronounced (2-fold and 3-fold,respectively). MCL-101 possessed almost the same affinity for the μ andκ opioid receptors as cyclorphan, but MCL-101 had greater κ/δselectivity (18-fold vs 4-fold). Further increasing the size of the ringled to a loss in binding affinity. Consistent with this observation, theN-cyclohexylmethyl derivative 21 (MCL-105) displays very low affinityfor the three opioid receptors.

Surprisingly, the N-propargyl derivative 9 (MCL-117) and theN-(3-iodoprop-(2E)-enyl) derivative 34 (MCL-118) exhibited unexpectedlyhigh affinity for the μ and κ opioid receptors with K_(i) values in thepicomolar range. In fact, these two compounds are among the most potentligands for the μ and κ opioid receptors identified to date. Compounds 9and 34 had the same high affinity for the μ opioid receptor, but 34displayed 10-fold decreased affinity for the κ and 43-fold decreasedaffinity for the δ opioid receptor in comparison to compound 9. TheN-(3-iodoprop-(2Z)-enyl) derivative 35, however, displayed dramaticallydecreased (100-fold and 17-fold) affinity for the μ and κ receptorsrelative to 34. The N-isopropyl derivative 4 (MCL-108) showed muchhigher (14-fold) affinity for the κ receptor but lower (2-fold) affinityfor the μ receptor than levorphanol. Replacement of the methyl with anallyl group 8 (MCL-113, levallorphan) resulted in 15-fold increase inaffinity for the κ opioid receptor and almost no changes in affinity forboth of the δ and μ opioid receptors. The N-(3-fluoropropyl) derivative3 (MCL-107) also displayed very high affinity for all three opioidreceptors (K_(i)=0.18 nM, 0.85 nM, and 0.083 nM for the μ, δ, and κreceptor, respectively).

The N-methoxyethyl derivative δ (MCL-110) was found to have highaffinity for the κ and μ opioid receptors (K_(i)=0.094 nM and 0.11 nM,respectively). Replacement of methoxyethyl with ethoxyethyl resulted ina 2-fold and 4-fold loss in affinity for the μ and κ opioid receptors,respectively. The N-phenoxyethyl derivative 13 (MCL-127) exhibiteddecreased affinity for all three opioid receptors relative to themethoxyethyl derivative 6.

Without intending to be bound by any theory, it appears that the size ofthe ether chain affects the affinity for the three opioid receptors. TheN-methoxymethyl and N-fluoropropyl derivatives of normetazocine werefound to bind nonselectively, with high affinity for the μ and κreceptors. The N-furanylmethyl derivative 22 (MCL-119) displayed highaffinity for the μ and κ receptors (K_(i)=0.54 nM and 0.13 nM,respectively). Replacement of the furanylmethyl group with thienylmethylresulted in decreased affinity for all three opioid receptors, but thisdecrease was most pronounced for the δ opioid receptor (6-fold vs.2-fold). Thus, the N-thienylmethyl derivative 23 (MCL-120) displayedgood selectivity for the μ and κ receptors versus δ receptor (κ/δ=160,μ/δ=14).

The N-benzyl derivative 7 (MCL-111) showed dramatically decreasedaffinity at all three opioid receptors relative to 22 and 23. Adding onemore methylene unit between the nitrogen and the phenyl ring (i.e., thephenethyl derivative 24) led to a great increase in binding affinity.The increase is 130-fold and 16-fold for the δ and μ opioid receptors,respectively.

The N-cyanoethyl derivative 11 (MCL-125) displayed increased affinity(10-fold) for the κ opioid receptor as compared with levorphanol (theN-methyl derivative). Replacement of the 2-cyanoethyl with a3-cyanopropyl group caused few changes in binding affinity for all threeopioid receptors. However, the N-trifluoropropyl derivative 12 haddecreased affinity for the μ and δ receptors and similar affinity forthe κ receptor relative to levorphanol.

The three Mannich base derivatives 26-28 showed similar binding profileswith good affinity for the μ opioid receptor and low affinity for boththe κ and δ opioid receptors. Reduction of the keto group to secondaryalcohol resulted in loss in binding affinity for the three opioidreceptors. Again without wishing to be bound by any theories, it seemsthat a hydroxyl group in the N-substituent interferes with theinteraction of the ligand with the opioid receptors, probably due to thehydroxyl group's hydrogen-donating property.

In conclusion, the N-substituent of morphinan had significant effect onthe binding affinity and selectivity for the three opioid receptors.These N-substituted derivatives exhibited a strong preference for μ andκ versus δ binding. The N-(3-fluoropropyl) 3 (MCL-107), N-methoxyethyl 6(MCL-110), the N-propargyl 9 (MCL-117), and the N-(3-iodoprop-(2E)-enyl)34 (MCL-118) derivatives possessed high affinity for the μ and κ opioidreceptors. In particular, the N-propargyl analogue 9 (MCL-117) and theN-(3-iodoprop-(2E)-enyl) analog 34 (MCL-118) showed very high affinityfor the μ and κ opioid receptors with K_(i) values in the picomolarrange. As noted above, the new compounds can be assayed for in vivoactivity using, for example, the tail flick assay as described byNeumeyer et al. (J. Med. Chem., 43:114-122, 2000) and McLaughlin et al.(J. Pharmacol. Exp. Ther., 289:304-311, 1999), and/or the acetic acidwrithing test described by Neumeyer et al. (J. Med. Chem., 43:114-122,2000) and Xu et al. (J. Pharmacol. Exp. Ther., 279:539-547, 1996).

Preparation and Administration of Pharmaceutical Formulations

The new compounds for use in accordance with the present invention canbe formulated in a conventional manner using one or more physiologicallyacceptable carriers or excipients.

Agents used in the formulations and their physiologically acceptablesalts and solvates can be prepared for administration by variousmethods. For example, administration can be parenteral, e.g.,intravenous, subcutaneous, intramuscular, intracranial, intraorbital,ophthalmic, intraventricular, intracapsular, intraspinal,intracisternal, intraperitoneal, transmucosal; or administration can beoral. The compounds can be formulated in various ways, according to theroute of administration.

For oral administration, the formulations can take the form of, forexample, tablets or capsules prepared by conventional means withpharmaceutically acceptable excipients such as binding agents (forexample, pregelatinised maize starch, polyvinylpyrrolidone orhydroxypropyl methylcellulose); fillers (for example, lactose,microcrystalline cellulose or calcium hydrogen phosphate); lubricants(for example, magnesium stearate, talc or silica); disintegrants (forexample, potato starch or sodium starch glycolate); or wetting agents(for example, sodium lauryl sulphate). The tablets can be coated orencapsulated (such as in a coating of hard gelatin or cyclodextran)using methods well known in the art (see, e.g., Baker, et al.,“Controlled Release of Biological Active Agents,” John Wiley and Sons,1986).

Liquid preparations for oral administration can take the form of, forexample, solutions, syrups or suspensions, or they can be presented as adry product for constitution with water or other suitable vehicle beforeuse. Such liquid preparations can be prepared by conventional means withpharmaceutically acceptable additives such as suspending agents (forexample, sorbitol syrup, cellulose derivatives or hydrogenated ediblefats); emulsifying agents (for example, lecithin may serve thisfunction, or acacia); non-aqueous vehicles (for example, almond oil,oily esters, ethyl alcohol or fractionated vegetable oils); andpreservatives (for example, methyl or propyl-p-hydroxybenzoates orsorbic acid). The preparations can also contain buffer salts, flavoring,coloring and sweetening agents as appropriate. Preparations for oraladministration can be suitably formulated to give controlled release ofthe active compound.

For buccal or sublingual administration the formulations can take theform of tablets or lozenges formulated in conventional manner.

The formulations can be prepared for parenteral administration byinjection, for example, by bolus injection or continuous infusion.Formulations for injection can be presented in unit dosage form, forexample, in ampoules or in multi-dose containers, with an addedpreservative. The formulations can take such forms as suspensions,solutions or emulsions in oily or aqueous vehicles, and can containformulatory agents such as suspending, stabilizing and/or dispersingagents. Alternatively, the active ingredient can be in powder form forconstitution with a suitable vehicle, for example, sterile pyrogen-freewater, before use.

The formulations can also be prepared in rectal compositions such assuppositories or retention enemas, for example, containing conventionalsuppository bases such as cocoa butter or other glycerides.

The formulations can also be provided as a depot preparation. Such longacting formulations may be administered by implantation (for examplesubcutaneously or intramuscularly) or by intramuscular injection. Thus,for example, the formulations can be prepared with suitable polymeric orhydrophobic materials (for example as an emulsion in an acceptable oil)or ion exchange resins, or as sparingly soluble derivatives, forexample, as a sparingly soluble salt.

Because the action of the new compounds is in the central nervoussystem, delivery techniques can be designed to permit or to enhance theability of the formulation to cross the blood-brain barrier. Suchtechniques are known in the art (for example, see PCT WO 89/10134,Cloughesy and Black, J. Neurooncol., 26:125-132, 1995; and Begley, J.Pharm. Pharmacol., 48:136-146, 1996, all of which are incorporatedherein in their entirety). Components of a formulation can also bemodified (e.g., chemically) using methods known in the art to facilitatetheir entry into the CNS.

In some cases, it may be desirable to deliver a compound formulationdirectly to the nervous system, especially when one or more componentsof a formulation do not cross the blood-brain barrier. Examples of suchmethods are intraventricular injection (Kordower et al., Exp. Neurol.,124:21-30, 1993) or installation of an osmotic pump (e.g., an Alzet®pump). Another example of such a method is to surgically place an Omayareservoir-shunt with in-line filter into the cisternal space. A compoundformulation in an appropriate excipient (e.g., phosphate-bufferedsaline) is instilled into the shunt by injection on a prescribed basis.In all cases, consideration is given to the appropriate formulation usedfor specific forms of delivery.

For administration by inhalation, a formulation is delivered, forexample, as an aerosol spray with the use of a suitable propellant, forexample, dichlorodifluoromethane, trichlorofluoromethane,dichlorotetrafluoroethane, carbon dioxide, or other suitable gas. Othersuitable methods of nasal delivery known in the art can be used,including those that facilitate delivery of a predetermined dosage.

The formulations can be presented in a pack or dispenser device, whichmay contain one or more unit dosage forms containing the activeingredient. The pack may, for example, comprise metal or plastic foil,such as a blister pack. The pack or dispenser device can be accompaniedby instructions for administration.

The therapeutic formulations of the invention can also contain a carrieror excipient, many of which are known to skilled artisans. Excipientsthat can be used include buffers (for example, citrate buffer, phosphatebuffer, acetate buffer, and bicarbonate buffer), amino acids, urea,alcohols, ascorbic acid, phospholipids, proteins (for example, serumalbumin), EDTA, sodium chloride, liposomes, mannitol, sorbitol, andglycerol. Suitable pharmaceutical carriers for intravenous and otherparenteral administration include, for example, sterile water,physiological saline, bacteriostatic saline (i.e., saline containingabout 0.9% mg/ml benzyl alcohol), phosphate-buffered saline, Hank'ssolution, or Ringer's lactate.

Suitable carriers for topical administration include commerciallyavailable inert gels, liquids supplemented with albumin,methylcellulose, or a collagen matrix. Typical of such formulation areointments, creams, and gels. Preferred carriers for topicaladministration are those that facilitate penetration of the skin by thenew compound.

Methods for making such formulations are well known and can be found in,for example, Remington's Pharmaceutical Sciences (Gennaro, ed., Williams& Wilkins, Baltimore, Md.). The compounds described herein can also beadministered as at least one physiologically acceptable salt such as achloride salt, a bromide salt, or an acetate salt.

Treatment with the New Compounds

In one example of the use of the new compounds and methods, a cocaineaddict is treated with one of the new drugs, given either orally orsystemically. Once the half-life of the drug is determined usingwell-known methods, a dosing regimen (including dosage and dosingfrequency) is established. In clinical trials of the drugs, tests areused to determine efficacy (defined, for example, as effectiveness incausing a person treated with the drug to stop using cocaine). Levels ofcocaine in the body would also be monitored in the clinical trials.

A therapeutically effective amount of the compound is a quantity ofcompound that, after being administered to an individual who has, forexample, an addiction to cocaine, brings about an amelioration of thedisease processes and conditions associated with the addiction withoutcausing unacceptable side effects.

The practitioner can determine the appropriate dosage for administrationto a human or experimental animal patient. The amount of a compound thatis administered will depend on a number of factors, including thegeneral health, size, age, and gender of the individual, as well as theroute of administration. It will also depend on the degree and severityof the individual's addiction. Typically, however, between about 100 μgand 5.0 g, e.g., 0.01 to 10 mg/kg, of the compound can be administeredto the individual per day. For example, about 1 to 1000 mg (e.g., 1 to100 mg or 1 to 30 mg) can be administered orally (e.g., in the form of apill, tablet, syrup, suspension, or capsule) or nasally (e.g., in theform of an inhalant) each day. The compound can also be administeredintravenously (e.g., by injection) into the systemic vascularcompartment. Still other appropriate modes of administration includesystemic administration, intramuscular, intradermal, subcutaneous,intraperitoneal, and topical administration.

Imaging with the New Compounds

Morphinans labeled, e.g., with isotopes of fluorine-18 or iodine-123,are useful for studying how brain opioid receptors change when, forexample, substance abusers undergo drug withdrawal treatment programs.Positron emission tomography (PET) and single-photon emission tomography(SPECT) scans can be used for comparing changes in opioid receptorbinding from baseline, through drug withdrawal, and through treatment.By comparing the timeline of these changes to changes in patient abusepatterns, researchers can predict time to relapse.

Successful visualization of receptors with PET or SPECT requires aligand that possesses both high affinity and low nonspecific binding. Ofthe commonly used positron-emitting isotopes, fluorine-18 (¹⁸F) offersconsiderable advantages, including a relatively long half-life (109minutes) that permits imaging when receptor-specific binding is at itshighest. Iodine-123 (¹²³I; half-life=13 hours) offers similar advantagesfor SPECT imaging. In view of their high affinity and low nonspecificbinding, compounds 3 and 10, which include fluorine atoms, and compounds34 and 35, which include iodine, are particularly well suited for use inPET and SPECT imaging, respectively. Other compounds in FIGS. 1A and 1Bcan also be used if properly labeled.

EXAMPLE

The following example, while not limiting the scope of the inventiondescribed in the claims, provides additional guidance for the use of thenew compounds for imaging.

The new morphinans, when properly labeled, e.g., with isotopes offluorine-18 and/or iodine-123, are useful for studying how brain opioidreceptors change when, for example, substance abusers undergo drugwithdrawal treatment programs. In this example,[123-I](−)-3-hydroxy-N-(E)-iodoallylmorphinan ([123-I]-MCL-118) wasprepared and evaluated by measuring SPECT regional brain uptake in ababoon brain.

(−)-3-hydroxy-N-(E)-tributylstannylallylmorphinan was prepared usingtechniques reported in Neumeyer et al., Bioorg. Med. Chem. Lett.,71:2735 (2001), was converted to the 123-I labeled compound MCL-118 bythe procedure of Baldwin et al., Nucl. Med. Biol., 20:597 (1993), aprocedure used for the conversion of methyl3-beta-4-tributylstannylphenyl)tropane-2-beta-carboxylate to[123-I]-beta-CIT.

The radiopharmaceutical was formulated in sterile isotonic salinecontaining about 1 mL L-ascorbic acid and 5% ethanol, pH was 6.5. 1.09mCi of the radiopharmaceutical was administrated through an intravenousline. Data were acquired with a brain-dedicated SPECT camera performedwith the AS-SPECT device (Digital Scintigraphics, Cambridge, Mass.). Thebrain activity (KBg/mL) and distribution over four hours is shown in thegraph in FIG. 5. In the graph, FC stands for the frontal cortex,PC—Piriform Cortex, BG—Basal Ganglia, CB—Cerebellum, HA—Hypothalamus,OC—Occipital Cortex, TIC—Temporal Cortex, and CC—Cengulate Cortex, whichare all areas of the brain.

The data show high uptake within 15-30 minutes in those areas of thebrain (OC, thalamus, brain stem, CC, and PC) containing the highestconcentration of kappa and mu receptors. In addition, theradiopharmaceutical is almost completely washed out in 4 hours from allareas of the brain.

OTHER EMBODIMENTS

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

1. A compound of Formula I,

wherein R is 3-fluoropropyl (3); 2-ethoxyethyl (5); 2-methoxyethyl (6);3,3,3-trifluoropropyl (10); 3-cyanopropyl (12); (2-furyl)methyl (22);3-(2-thienyl)-3-oxo-propyl (26); 3-(2-furyl)-3-oxo-propyl (28);3-(2-thienyl)-3-hydroxy-propyl (29); 3-(2-furyl)-3-hydroxy-propyl (31);3-idoprop-(2E)-enyl (34); or 3-idoprop-(2Z)-enyl (35);3-(tri-n-butylstannyl)-prop-(2E)-enyl (32);3-(tri-n-butylstannyl)-prop-(2Z)-enyl (33); or a salt thereof.
 2. Thecompound of claim 1, wherein R is 3, 5, 6, 10, 12, 26, 28, 29, 31, 34,or 35, or a salt thereof.
 3. The compound of claim 2, wherein R is
 3. 4.The compound of claim 2, wherein R is
 5. 5. The compound of claim 2,wherein R is
 6. 6. The compound of claim 2, wherein R is
 10. 7. Thecompound of claim 2, wherein R is
 12. 8. The compound of claim 2,wherein R is
 34. 9. The compound of claim 1, wherein R is
 35. 10. Apharmaceutical formulation comprising the compound of claim 1, and aphysiologically acceptable excipient.
 11. A pharmaceutical formulationcomprising the compound of claim 2, and a physiologically acceptableexcipient.
 12. A method of single-photon computed tomography (SPECT)imaging of opioid receptors in a subject, the method comprising:obtaining a compound of claim 1 and labeling the compound with aradioactive label, administering the labeled compound to the subject;and obtaining scans with a SPECT camera to image the opioid receptors.13. The method of claim 12, wherein the radioactive label is ¹²³I. 14.The method of claim 12, wherein R is
 34. 15. The method of claim 12,wherein R is
 35. 16. A SPECT imaging reagent comprising a ¹²³I-labeledcompound of Formula I,

wherein R is ¹²³I-labeled 3-iodoprop-(2E)-enyl (34) or3-idoprop-(2Z)-enyl (35).
 17. A method of positron emission tomography(PET) imaging of brain opioid receptors in a subject, the methodcomprising: obtaining a compound of claim 1 and labeling the compoundwith a radioactive label; administering the labeled compound to thesubject; and obtaining brain scans with a PET camera to image the opioidreceptors.
 18. The method of claim 17, wherein the radioactive label is¹⁸F.
 19. The method of claim 17, wherein R is
 3. 20. The method of claim17, wherein R is
 10. 21. A PET imaging reagent comprising an ¹⁸F-labeledcompound of Formula I,

wherein R is ¹⁸F-labeled 3-fluoropropyl (3) or 3,3,3-trifluoropropyl(10).
 22. A method of treating a patient addicted to cocaine, the methodcomprising administering to the patient an effective amount of acompound of claim 1 or one or more compounds of Formula I,

wherein R is 2-methylpropyl (4); 2-propenyl (8); 2-propynyl (9);2-cyanoethyl (11).
 23. The method of claim 22, wherein R is 3, 5, 6, 10,12, 26, 28, 29, 31, 34, or
 35. 24. The method of claim 22, wherein R is4, 8, 9, or
 11. 25. The method of claim 22, wherein R is 3, 9, or 34.